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l AUS- 11, 1959 JQ D. JORDAN 2,899,514.

SWITCHES Filedsept. 2o, 194s a L ,4 A\' l F16. 6; z creo/wc var/zal.

FIG. 3. Men/vs i@wwv 5' INVENTOR 2 -22 9 v 20 .JAMES D. JORDAN ATT NEYSWITCH James D. Jordan, Washington, D.C., assignor to the United Statesof America as represented by the Secretary of the Navy ApplicationSeptember 20, 1943, Serial No. 503,146

6 Claims. (Cl. 200-80) This invention relates to a switch for use inelectrically fuzed rotating projectiles, and more particularly to anovel switch which operates to break a circuit for arming a projectilefuze.

In electrically operated projectile fuzes, an electrically rcd squib isgenerally used to detonate a booster charge which, in turn, explodes themain charge of the projectile. In order to prevent premature tiring ofthe squib by accidental actuation of the fuze, a short circuit aroundthe squib is provided so that current which would otherwise operate thesquib is by-passed around the squib, and the fuze remains unarmed aslong as the short circuit is unbroken. Upon tiring the projectile from agun, an unshorting switch in the circuit is actuated to rupture theshorting circuit and arm the squib. y

One object of the invention is to provide a novel unshorting switch forthe above-described use, which is operable only upon firing of theprojectile from a gun, or the like, and which will not be operated bydropping, jolting7 or tumbling of the projectile.

A further object of the invention is to provide a device of thecharacter described in which the centrifugal force caused by rotation ofthe projectile in its flight is utilized to break the shorting circuit.

A further object of the invention is to provide a device of thecharacter described which will be simple and positive in operation andadapted to large scale manufacture.

These and other objects of the invention will be obvious from thefollowing description and the accompanying drawing, in which Fig. l is alongitudinal sectional view of one form of the new unshorting switch,with the parts in their unarmed positions;

Fig. 2is a view similar to Fig. 1, but with the parts in their armedpositions;

Fig. 3 is a cross sectional view taken on line 3--3 of Fig. l;

Fig. 4 is an exploded view of the switch omitting the tubular casing andthe end plugs,

Fig. 5 is a detailed longitudinal sectional view of a portion of anotherembodiment of the invention; and

Fig. 6 is a diagrammatic of the forward portion of a projectile,embodying the invention.

Referring rst to Fig. 6 of the drawing, there is shown a projectile 7having mounted therein an electronic control means 8 (which, forexample, can comprise a radio proximity fuze including a thyratron), asquib and detonator unit 9 for tiring the projectile 7 when the propersignal is received from the electronic control means 8, and the tubularcasing 10 which includes the switch of the present invention.

In the embodiment of the invention shown in Figs. 1 through 4, thetubular casing 10 of insulating material is provided at its ends withplugs 11 and 12 through which electrical connectors 13 and 14,respectively, extend. In the interior of the casing are cylindricalinertia elements 15 and 16 of electrically conducting material, theinner ends of the inertia elements being separated by United StatesPatent O rice a washer 17 of nonconducting material. The inertiaelements 15 and 16 have axial passages 15a and 16a which receive andsecure the ends of a frangible, electrically conducting element 18extending through the center of washer 17 and providing an electricalconnection between the inertia elements. The two spaced and insulatedinertia elements 15 and 16 are thus initially and normally united by aseparable joint, including the connecting pin or electrical conductor18, and the safety switch thus formed is opened when the separable jointis disrupted or separated under centrifugal force created by a spinningprojectile. The inner ends of connectors 13 and 14 extend into the outerends of the axial passages 15a and 16a, respectively, the portion ofeach connector lying between the adjacent end plug and the adjacentinertia element being formed as a helix or spring, as shown at 13a and14a, for a purpose to be explained presently.

In the operation of this embodiment of the invention, the device withthe parts in their unarmed positions, as shown in Fig. l, is mounted inrotating projectile 7 transversely of the axis of rotation of theprojectile, with the mid-point of the casing lying substantially at theaxis of rotation of the projectile.

Connectors 13 and 14 are connected across a squib (not shown) so thatthe circuit comprising connector 14, inertia element 16, frangibleelement 18, inertia element 15 and connector 13 forms a short circuitaround the squib. As long as this short circuit is unbroken, it willprevent tiring of the squib in case of accidental electrical operationof the fuze. The helical portions of connectors 13 and 14 act ascompression springs and tend to hold the inner ends of inertia elements15 and 16 against washer 17, as shown in Fig. 1. The purpose of thesesprings is to prevent accidental separation of the inertia elements,with resulting rupture of frangible element 18, by dropping or joltingof the device. Should the projectile 7 be dropped on its side, that is,in a direction longitudinally of the casing 10, the inertia elements 15and 16 will move together in that direction, compressing the spring 13aor 14a at one end of the casing and extending the other spring. If theprojectile 7 is dropped in a direction transversely to the casing 10,there will be no force tending to separate the inertia elements 15 and16. The strength of the springs and of frangible element 18 determinethe magnitude of the speed of rotation necessary to operate the device,and these strengths are adjusted so as to prevent rupture of element 18by rotations slower than that which takes place when the projectile islired from a gun. Thus it is apparent that the device is safe againstaccidental actuation of the unshorting switch.

When a projectile 7 containing the device is tired from a gun, the highspeed of rotation of the projectile 7 in its flight sets up largecentrifugal forces which act on the inertia elements 15 and 16,resulting in outward movement of these elements away from each other andfracture of the frangible element 18, as shown in Fig. 2. Uponfracturing of the frangible element, the shorting circuit is broken andthe squib is armed.

The modification of the invention shown in Fig. 5 is the same as theembodiment shown in Figs. 1 through 4 except that the frangibleconnection 18 between the inertia elements is replaced by anelectrically conducting projectile 19 screwed into inertia element 20with its projecting end extending into a recess 21 in inertia element22, the insulating washer 17a separating the inertia elements as in thedevice shown in Figs. 1 through 4.

The operation of the device shown in Fig. 5 is similar to the operationof the device shown in Figs. 1 through 4, except that separation ofinertia elements 20 and 22 by centrifugal force on tiring of theprojectile moves projection 19 out of contact with inertia element Z2 torupture the shorting circuit. It will be understood that the inertiaelements 20 and 22 are normally urged inwardly by the springs 13a and14a (Fig. 1).

If desired, separate springs may be provided at the outer ends of theinertia elements, instead of forming the conductors 13 and 14 in ahelical shape. If separate springs are used, it is necessary to provideenough slack wire between the outer end of each inertia element and theadjacent plug to permit movement of the inertia elements toward theopposite end of the casing without danger of the connector breaking.

An important feature of the invention is that the two inertia elementswill always tend to move together as a unit in the casing when they aremoved by any force other than the centrifugal force caused by rotationof the projectile. As long as the inertia elements move as a unit, thereis no danger of breaking the electrical connection between them. Thetendency of the inertia elements to move as one element, except whenacted upon by centrifugal force, is increased by the springs 13a, 14awhich urge the inertia elements together.

It is to be understood that the switch is susceptible of variousmodifications within the scope of the invention. For example, the switchmay be arranged so that the inertia elements act under centrifugal forceto close a circuit rather than break a short circuit.

l. In a centrifugal safety device for use in a rotating projectile, atubular casing of nonconducting material mounted transversely of theprojectile, an insulating plug at each end of the casing, two inertiaelements Ymounted in said casing for movement longitudinally of thecasing, said inertia elements being of conducting material, aninsulating washer separating said inertia elements,a frangible,conducting element extending through said washer and having its endsconnected to said inertia elements, and a connector attached to theouter end of each of said inertia elements and extending through theadjacent plug, the portion of each connector lying between the adjacentplug and the adjacent inertia element forming a spring to resist outwardmovement of the inertia elements, whereby the inertia elements and thefrangible connector are movable as a unit in either direction againstone of the springs, and said frangible element is ruptured by outwardmovement of the inertia elements under centrifugal force.

2. In a centrifugal safety device for use in a rotating projectile, atubular casing of nonconducting material mounted transversely of theprojectile, an insulating plug at each end of said casing, two inertiaelements mounted in said casing for movement longitudinally of thecasing, said inertia elements being of conducting material, aninsulating washer separating said inertia elements, conducting meansextending through said washer and forming an electrical connectionbetween said inertia elements, a connector extending from the outer endof each of said inertia elements through the adjacent plug, the portionof the connector lying between the plug and the adjacent inertia elementforming a spring to resist outward movement of the inertia elements,whereby the inertia elements and said conducting means are movable as aunit in either direction against one of the springs, and said electricalconnection between the inertia elements is broken by outward movement ofthe inertia elements under centrifugal force.

3. In a centrifugal safety device for use in a rotating projectile, atubular casing of nonconducting material mounted transversely of theprojectile, an insulating plug at each end of said casing, two inertiaelements mounted in said casing for movement longitudinally of saidcasing, said inertia elements being of conducting material, the innerend of one of said inertia elements having a recess therein, aninsulating washer separating said inertia elements, a conducting elementprojecting from the other inertia element and extending through theWasher into said recess to connect said inertia elements electrically, aconnector extending from the outer end of each of said inertia elementsthrough the adjacent plug, the portion of the connector lying betweenthe 'plug and the adjacent inertia element forming a spring to resistoutward movement of the inertia elements, whereby the inertia elementsand said conducting element are movable as a unit in either directionagainst one of the springs, and said conducting element is withdrawnfrom the recess by outward movement of the inertia elements undercentrifugal force.

4. In a centrifugal safety device for use in a rotating projectile, atubular casing adapted to be mounted transversely of the projectile, apair of inertia elements slidable longitudinally in the casing, saidelements being of conducting material insulated from the casing andadapted for electrical connection outside the casing, biasing means forurging said elements together, and means normally connecting saidelements electrically in the casing and operable to break the electricalconnection in the casing between said elements upon outward movement ofsaid elements away from each other under centrifugal force, saidelements and connecting means being movable normally as a unit in thecasing against the biasing means to maintain said electrical connection.

5. In a centrifugally operated safety device for use in a rotatingprojectile, a pair of electrically conducting inertia elements movabletransversely of the axis of rotation of the projectile, a frangible,conducting element directly and integrally connecting said inertiaelements, so that said inertia elements and said frangible elementnormally move as one unit, and biasing means for urging said inertiaelements together, said inertia elements, said frangible element, andsaid biasing means constituting part of an electric circuit whereby uponthe outward movement of said inertia elements under the influence ofcentrifugal forces, said frangible element is ruptured andsimultaneously said inertia elements are released and said electriccircuit is interrupted.

6. The combination in a oentrifugally operated circuitbreaker, with anenclosing casing, of two spaced movable and insulating inertia elementsforming part of an electric circuit, connecting means forming aseparable joint uniting said inertia elements electrically as Well asmechanically, said connecting means being frangible, and resilient meanswithin the casing for absorbing bodily movement of the jointedstructure.

References Cited in the file of this patent FOREIGN PATENTS 18,869 GreatBritain Nov. 14, 1910 245,766 Great Britain Jan. 4, 1926 358,307 FranceOct. 10, 1905

